Well, looks like the fix was not really tough! We have just fixed and it will be available on the upcoming 4.2.0 release, so stay tuned!

For premium subscription users, the fix would already be available, but it has been made in the branch we are merging ExtJS 6.2.1 (unstable), but it would be easy to cherry-pick the change to current master if anyone needed this fixed immediately!

Thanks again for reporting us the issue! Looking forward to your feedback about the workaround provided!